import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum F_INF = sqrt(0.81L / (1.0L - 0.81L)) / (0.9L / (1.0L - 0.9L));
real F(int n) {
  real numer = 0.0L, denom = 0.0L;
  foreach (i; 1 .. n + 1) {
    numer += 0.81L^^i;
    denom += 0.9L^^i;
  }
  return sqrt(numer) / denom;
}
real f(int n) {
  return (F(n) - F_INF) / (F(1) - F_INF) * 1200.0L;
}

real g(real x) {
  return 2.0L^^(x / 800.0L);
}
real gInv(real y) {
  return (log(y) / log(2.0L)) * 800.0L;
}

void main() {
  try {
    for (; ; ) {
      const N = readInt();
      auto RPerf = new real[N + 1];
      foreach (i; 1 .. N + 1) {
        RPerf[i] = readReal();
      }
      
      real numer = 0.0L, denom = 0.0L;
      foreach (i; 1 .. N + 1) {
        numer += g(RPerf[i]) * 0.9L^^i;
        denom += 0.9L^^i;
      }
      const ans = gInv(numer / denom) - f(N);
      writefln("%.0f", ans);
    }
  } catch (EOFException e) {
  }
}